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92                                   SODIUM ALUMINATE

the residue should give the reactions for potassium in the flame and with
ta.rtar.ic acid).

AgN();, = 169-94 (170)

Transparent, colourless crystals, alterable in the light in presence of
organic matter, soluble in 0-5 part of water, in alcohol o/ in ether. The
tests to be made are :

1.  Solubility.i part, with 0-5 part of water, should give a solution
which is clear and remains so after addition of alcohol.

2.  Extraneous Salts.-.......i gram, dissolved in 40 c.c. of water, is treated

with 6 c.c. of N-hydrochloric acid ; the silver chloride is allowed to deposit
in the hot and the filtered liquid evaporated and the residue ignited gently ;

no appreciable residue should remain-.....merely a faint, black stain of reduced



Na('.>U.,Oa + 'ill'/)    : i'.U)-i2

(5                   M         ll        J       I       */          ^                           J

Colourless crystals extremely soluble- in water and in 25 parts of 90%
alcohol; also the anhydrous (Fused sodium tic-dtite) in greyish, fused
masses. The pure salt should answer the following tests :

1.  Reaction.- -The  i : 10 solution  should  be  clear  and   should  not
redden phenolphthaleiii and should react slightly alkaline with litmus paper.

2.  Empyreumatic or Tarry Substances.......0-5 gram should dissolve

in pure cone, sulphuric acid without browning.    0-5 gram, dissolved in
water, acidified with 5 c.c. of pure- dilute sulphuric acid (i : 3) and treated
with i drop of N/io-permanganate, should have a persistent pink colour

3.  Extraneous Metals.   The   i ; 10 solution,  acidified  with  hydro-
chloric acid, should not give a, blue colour with potassium feiTocyanide (iron)
and should not change with hydrogen sulphide (/n'tiry -ni-ehds) ;   acidified
with acetic acid, it should undergo no change with ammonium oxalato
(lime) ;  acidified with nitric acid, it should give no turbidity, even after
standing, with barium chloride (Mtlfi/uttcs), and with silver nitrate should
give at most a slight opalcseence (chlorides).

AI-jNaA :-164-2

This is sold in white crystalline! masses, or as a. moist paste, or in solution.
It is soluble in water but the solution becomes cloudy in the air. The
common impurities are insoluble substances, silica, and iron (sec i -j, below),
and the value depends on the content of alumina and sodium oxide (ace 4).

1. Insoluble Substances. -10 20 grams are dissolved in hot water
and the solution filtered through a tared filter,1 the insoluble part being

1 As it is an alkaline liquid it is best to use a filter of either lumkmt-d paper or other
similar good filter-paper.qual volume of cone,